Understanding Digital Projector Specifications

When selecting a data projector it is important to understand the different features and specifications in order to ensure that choose the model most appropriate to your requirements. Armed with a thorough understanding of the different options on offer you will be able to make sense of the complicated specification lists and choose the right device.
Brightness
One of the most important aspects of a projector’s performance is its brightness. In perfect conditions, with a completely dark room and a high quality reflective projector screen you can achieve reasonable image quality on a low-brightness device. However, in the real business environment we very rarely get such ideal conditions. Quite often the projector is used in meeting rooms with a high degree of ambient light from windows which ca not be covered or lights which can not be switched off. In these situations a projector with low brightness will produce a faint, washed out looking picture. For this reason it is a good idea to buy the brightest projector your budget permits.

Brightness is measured in ANSI (American National Standards Institute) lumens. The cheapest projectors offer brightness levels of 750 lumens, sometimes lower – these will produce very poor results and should be avoided if possible. High end projectors may offer up to and above 5000 lumens, but the middle ground of 1500 to 2000 lumens should be suitable for most business purposes.

Resolution
Just like a standard PC monitor, projectors have different pixel resolutions. The lowest resolution available is 640 by 480, although this is considered to be pretty much obsolete and it is increasingly difficult to find these models on sale. The lowest practical resolution currently available is 800 by 600 and although this does not seem particularly high, it is perfectly acceptable for most run of the mill presentation applications. The next step up is 1024 by 768 – which is currently the resolution most people use for their desktop monitors and therefore the most desirable. Higher resolutions are available up to 1920 by 1080 and beyond, while this kind of image quality is nice to have for graphically detailed computer games and suchlike, it is not considered essential for business applications. Manufacturers often refer to resolutions using their technical designations:

Unlike CRT monitors projectors are not good at displaying different resolutions, so if your laptop resolution is 800 by 600 and you plug it into a 1024 by 768 projector the image quality will suffer badly as the projector tries to stretch the lower resolution image to fit its own resolution.

Contrast Ratio
The contrast ratio is a measurement of the difference between the blacks and whites displayed by a projector. A high contrast ratio is good because it means the projector will be better at showing subtle colour differences in an image, but a low contrast ratio means that a picture made up of lots of dark shades will simply appear as one dark blob. Contrast ratios can vary between 300:1 and 3000:1, but the numbers can be a little misleading. A projector cannot project black light, the black parts of an image are simply areas of the screen that no light is projected onto.

In a completely dark room with absolutely no ambient light, the black areas will appear to be perfectly black – because that is how the screen looks with no light being projected onto it. But if, as is more often the case, there is a bit of ambient light, then the black areas will be a dark grey rather than perfect black. A contrast ratio of 1000:1 or 1500:1 will be adequate for most normal conditions – and if you only plan to show Power Point slides you could easily live with an even lower ratio. Higher contrast ratios will not make a particularly noticeable difference in anything other than perfectly dark conditions. In short, more contrast is better but it should not be your main purchasing criteria.

Inputs
Depending on what you intend to use a projector for, it may be important to pay attention to the type of signal inputs it can accept. Most devices will have a standard VGA input for connecting to a computer – this is the same type of cable that connects your monitor to your PC. Portable and low end devices are unlikely to have anything else apart from a VGA connector, since they are unlikely to be used for anything other than displaying presentations from a laptop. More advanced models may feature other inputs such as composite connectors – these are commonly used in audio visual equipment such as camcorders, DVD players and video games consoles. Composite inputs consist of three round connectors each colour coded red, yellow and white. Another type of connector commonly used in audio visual applications is S-Video – a small round plug with five pins. S-Video connectors offer better image quality than composite connectors. If a projector is likely to be taken home for personal use at the weekends then it is important that it should feature one of these two connector types. You should easily be able to find an adaptor cable to make most A/V and home entertainment equipment with either S-Video or composite connectors. There are numerous other connectors which are used in more advanced equipment, and more expensive projectors will offer a wider range of inputs. If you have specialist AV equipment then you should check that any projector you plan to purchase has the required inputs – if in doubt ask the manufacturer.

Lens Features
The lens is one of the most important components of a projector, and there are lens features which can play a significant part in the performance of your device. Short throw lenses are especially useful for presentations in small meeting rooms because they allow a large image to be projected from quite a short distance. Without a short throw lens the only way to get a larger image is to move the projector further away from the screen. If you are considering a device with a short throw lens, find out what its maximum image size is and at what distance from the screen it can produce that size.

For projecting in rooms with awkward layouts a feature know as lens shift, or side-shot, is especially useful. This allows the position of the projected image to be altered without having to move the projector itself and is used in situations where the projector screen is not directly in front of the projector position. Essentially, the projector displays the image at angle off to the side whilst automatically correcting the image format so that it does not appear distorted. This feature is especially useful when using a projector in the home, where users are rarely able to position the projector directly in front of the place they want the image to be displayed.

Aspect Ratio
As business projectors increasingly find themselves being appropriated for non-business purposes out of office hours, features such as wide-screen capability have begun to creep in. Most projectors will feature an aspect ratio of either 4:3 (normal business format) or 16:9 (widescreen). A 16:9 format projector will have no problems displaying presentations and other business material since it will simply leave the unused areas at the side of the image blank. On the other hand a 4:3 aspect ratio projector will be able to display a widescreen movie, but it will have to reduce the overall size of the image to fit it into the display area.

Extra features
Increasingly projectors are being equipped with wireless capability which allows you to run presentations without having to get tangled up in cables. This feature is useful for relatively static slide by slide presentations, but for applications such as video the wireless connection may not be fast enough to keep up with the larger amount of data that needs to be transferred from the PC to the projector.

Another new feature which is becoming more popular is USB connectivity. One of the main advantages of this is that it allows users to run a PowerPoint presentation directly from a USB memory card completely eliminating the need for a laptop – you just plug the memory card into the projector and go. Sony offers a similar feature on some of its projectors, but using its proprietary Memory Stick.